1. Field of the Invention
This invention relates to improved self-locking adjust tongues for seat belt buckle assemblies.
2. Description of the Prior Art
In vehicles equipped with active seat belt systems, self-locking adjust tongues are commonly used. Center seats are frequently equipped with static lap belts, and, after buckling, these systems require the occupant to pull the loose end of the webbing exiting the adjust tongue to provide a snug fit about the pelvic region. The adjust tongue must be capable of preventing the loose end of the webbing from slipping in order to provide occupant protection under crash load conditions. Government regulations require that lock-up occur when specific angles between the ingressing webbing and the bottom of the tongue are experienced (e.g., at a minimum angle of 30.degree.). Conventional adjust tongues include a bar slidable in slots in laterally upstanding flanges, with the webbing being wrapped around the bar.
Continuous loop seat belt systems including retractors provided with tension eliminators are commonly used in the front outboard positions in U.S. vehicles. Adjust tongues are again an essential part of such systems. The tongue must be capable of sliding on the belt to provide proper fit to the occupant but must lock (that is disallow slippage of the webbing over the bar) under crash conditions to prevent any slack in the shoulder belt webbing from transferring to the lap belt.
Because of the critical nature of the lock-up angle, much care must be taken in maintaining smooth surfaces of the bar and slot interfaces. If the surfaces are not consistently smooth, inconsistent lock-up angles can be experienced. This is a difficult situation in such mass produced products and presently requires high tolerances and costly surface finishes. It would be desirable to provide consistent lock-up angles on these mass produced parts without the need to control the surface finish between the bar and the slots.